We use the present simple to talk about a general fact.
ex : truth, a proverb

(ex) The Sun rises in the east.
(ex) The Earth goes round the Sun.

We use the present simple to talk about a present state of affairs.

(ex) What do you do? I work for IBM.
(ex) She lives in the suburbs. (Don't forget the s)

When something happens all the time or repeatedly like habitual actions,
We use the present simple.

(ex) I come at 6 o'clock every evening.
(ex) How many times do you go to a cinema a week?

We use the present the present simple to talk about future timetables.

(ex) He starts for Sydney tomorrow evening.  
(= He will start for Sydney tomorrow evening.)